1. Field of the Invention
The present invention relates to a sheet original supply apparatus for supplying a sheet original to a predetermined position such as a reading portion of an image forming apparatus such as a copying machine, a laser beam printer and the like and for resting such a sheet original on the predetermined position. Further, the present invention relates to a reading apparatus and an image forming apparatus.
2. Related Background Art
FIG. 26 shows an example of a conventional sheet original supply apparatus. In FIG. 26, a sheet original P is supplied from an original tray 413 to a platen glass 422, where an image on the sheet original is read by an optical system 421 of a copying machine, and then the sheet original is discharged onto a tray 423.
In particular, a separation means 414, 415, supply rollers 416 for effecting regist correction, relay rollers 417, and an image tip end sensor S1 are arranged in order, and, by means of such supply means, the original is passed through the platen 422 from the right, during which the reading-through (in which the image is read while the sheet original is being moved) of the sheet original is performed to form the image.
However, with the above-mentioned conventional arrangement, when the reading-through of the sheet original is being effected while the sheet original is being passed through the platen 422, as a trailing end of the sheet original leaves the relay rollers 417, the load fluctuation acts on the sheet original P, thereby causing discrepancies in the image read at platen 422.
Further, in the above-mentioned conventional technique, the sheet originals P are separated one by one by the separation means 414, 415. When the skew-feed of the sheet original is corrected by abutting the separated sheet original against a nip between the supply rollers 416, since the rear portion of the sheet original is still remaining in the separation means 414, 415 and the separation roller 415 and the separation belt 414 are being rotated in directions shown by the arrows, respectively, as the sheet original is pulled by the supply rollers 416, the sheet original is subjected to a load, with the result that there arises slip between the supply rollers 416 and the original, thereby worsening the regist correction (i.e., causing the error in a sheet feeding amount of the sheet original fed by the supply rollers 416).
Further, a sheet feed path from the supply rollers (regist correction rollers) 416 to the image reading portion 422 becomes long because the relay rollers 417 must be positioned in such a path, with the result that the regist-corrected sheet original may become skewed (out of correct registration) in the path on the way to the image reading portion 422.